NASA researchers have discovered living microorganisms trapped inside crystals for as many as 60,000 years in Mexico’s Naica Mine cave system.

Penelope Boston of the federal agency’s Astrobiology Institute said that nearly 100 different sorts of microbes, most of which are bacteria, were discovered locked in Naica crystals for 10,000 to 60,000 years.

The huge crystals were discovered in the Naica mine in the northern Mexican state of Chihuahua, which is famous for producing lead, zinc and silver. It has huge crystals, some as many as 50 feet long.

Sharing the discovery of the ultra-hardy microorganisms, Boston said, “This has profound effects on how we try to understand the evolutionary history of microbial life on this planet.”

However, researchers are also concerned as it has indicated that bringing back samples collected during space missions in our solar system could allow dangerous extraterrestrial microorganisms to accidentally hitch a ride to our planet on a returning spaceship.

The discovery of the 60,000-year-old microbes was shared at a recently held conference of the American Association for the Advancement of Science.